Thursday, December 14, 2006

New Study Shows that Coronary Blood Flow is Not Impaired in Active Smokers, Much Less Passive Smokers; Statements of 38+ Anti-Smoking Groups are False

A new study published in this month's issue of The Journal of Nuclear Medicine reports that coronary blood flow is not reduced in young smokers, throwing into severe doubt the claim by 38+ anti-smoking groups that passive smoking reduces coronary blood flow (see: Morita K, Tsukamoto T, Naya M, et al. Smoking cessation normalizes coronary endothelial vasomotor response assessed with 15O-water and PET in healthy young smokers. The Journal of Nuclear Medicine 2006; 47:1914-1920).

The study used PET scans to measure myocardial blood flow in 14 young smokers with no evidence of heart disease and 12 age-matched nonsmokers. Active smoking was found not to affect coronary blood flow, as there were no significant differences in the measured myocardial blood flow between smokers and nonsmokers. The researchers did find a reduction in endothelium-mediated vasodilation, as blood flow in response to a cold pressor test was reduced in the smokers, which the authors conclude indicates endothelial dysfunction. Of note, this endothelial dysfunction was reversed within one month of smoking cessation.

According to the study: "There were no significant differences in myocardial blood flow at rest and during ATP infusion between smokers and nonsmokers."

The authors concluded that: "young healthy smokers have impaired coronary endothelial vasomotor dysfunction, which is reversible within 1 month after smoking cessation, and the improvement is preserved at 6 months after cessation. ... These findings indicate that coronary endothelial dysfunction may be reversible within 1 month after smoking cessation in healthy young smokers."

The Rest of the Story

This study demonstrates that the statements being made to the public by 38+ anti-smoking groups, indicating that secondhand smoke exposure reduces coronary blood flow, are not just deceptive - they are just plain wrong.

To suggest, as Americans for Nonsmokers' Rights (ANR) does, that 30 minutes of secondhand smoke impairs the ability of healthy young nonsmokers' hearts to get life-giving blood, seems to be inaccurate in light of the evidence presented in this paper. Even active smokers did not have a problem with myocardial blood flow in this study.

The numerous other claims made by anti-smoking groups, indicating that secondhand smoke reduces blood flow to the heart, are also inaccurate. The truth is that even active smoking, in the absence of heart disease, does not reduce blood flow to the heart. It is only endothelial function that is affected by tobacco smoke, not baseline coronary blood flow.

In light of this new research, it is now inexcusable for these anti-smoking groups to fail to retract these claims and apologize for misleading the public.

ClearWay Minnesota has apparently responded by removing from the internet its smoking ban manual which contained the fallacious statement that secondhand smoke reduces coronary blood flow in healthy young adults (although I'm aware of no acknowledgment of the mistake nor an apology for it). But at least it's a step in the right direction - getting the false health claim off its website and preventing the public from being misled any further.

There are now well over 30 anti-smoking groups that need to follow ClearWay's lead.

One other aspect of the study deserves mention. This research found that endothelial dysfunction induced by active smoking is reversible within one month following smoking cessation. If this is true, then certainly endothelial dysfunction induced by a 30-minute exposure to secondhand smoke is reversible.

This confirms that the statements being made by a number of health and anti-smoking groups, including the Office of the Surgeon General, that brief secondhand smoke exposure causes atherosclerosis, narrowing or hardening of the arteries, or heart disease are false.

If endothelial dysfunction in active smokers is quickly reversible, then it is also reversible in passive smokers, and thus a brief exposure cannot possibly lead to hardening of the arteries (atherosclerosis) and heart disease, despite what the Surgeon General told the public.

Because of the high-profile nature of the communication from the Surgeon General's report, the heavy reliance of the tobacco control movement on the Surgeon General for public education, and the intense publicity surrounding the report and high media response to the press release containing the untruthful statement, a correction and apology for that misrepresentation of the science is particularly important for the credibility of the tobacco control movement.

No comments:

About Me

Dr. Siegel is a Professor in the Department of Community Health Sciences, Boston University School of Public Health. He has 32 years of experience in the field of tobacco control. He previously spent two years working at the Office on Smoking and Health at CDC, where he conducted research on secondhand smoke and cigarette advertising. He has published nearly 70 papers related to tobacco. He testified in the landmark Engle lawsuit against the tobacco companies, which resulted in an unprecedented $145 billion verdict against the industry. He teaches social and behavioral sciences, mass communication and public health, and public health advocacy in the Masters of Public Health program.